There are a number of different technologies which have been used to create three-dimensional (3D) displays. Some of the technologies simulate depth using a planar display screen through visual effects and require glasses to be worn by onlookers. Volumetric displays, however, create a 3D light field within a volume which can be viewed by an onlooker without any requirement for special glasses. These volumetric displays may also be described as autostereoscopic because they create a 3D image which is visible to the unaided eye.
In an example of a volumetric display, different images (or different views of an object) are projected synchronously onto a rotating holographic mirror. The projection of the different images builds up a 3D image which can be seen from different viewpoints. Another example of a volumetric display uses a stack of switchable diffusers. Different depth images are projected in sequence onto the stack of diffusers, in order to simulate the 3D scene data which would be visible at different slices through the volume. Both these examples make use of the speed of refresh and user perceived visual continuity to enable a 3D image to be fused together.
The embodiments described below are not limited to implementations which solve any or all of the disadvantages of known volumetric displays.